Software defined networking (SDN) is a new form of network architecture in which the control plane is separated from the data plane and implemented as a software application. This architecture allows network administrators to have programmable logically centralized control of network traffic without requiring physical access to the network's hardware devices. Thus, SDN decouples network control (learning and forwarding decisions) from network topology (junctions, interfaces, and how they peer). Decoupling network control from network topology enables better routing decisions and resource utilization based on centrally collected and managed global network topology, states, and applications or traffic flow patterns. SDN may simplify network operations, where centralized controller can pre-specify alternate routing path and configure network equipment automatically, and global definitions per identity do not have to be matched to each and every interface location. The basic approach to achieve decoupling of the network control from the network topology is by applying globally aware and topology decoupled software control at the edges of the network. The assumption is that traditional topology-coupled bridging and routing drives the core of the network so that scalability, interoperability, high-availability, and extensibility of Internet Protocol (IP) networks can be maintained.
In one configuration of an SDN, the network control plane hardware is physically decoupled from the data forwarding plane hardware, e.g., a network switch forwards packets and a separate server or controller operates the network control plane. SDN may require some method for the control plane to communicate with the data plane. One mechanism to do so is through OpenFlow (OF) which is a standard protocol or interface for controlling networking switches. However, as SDN evolves rapidly, standards become incompatible, requiring dedicated network controllers for each version of the standards. For example, OpenFlow 1.2 is not backward compatible with OpenFlow 1.0. As a consequence, an OpenFlow 1.0 controller may be required to control OpenFlow 1.0 switches and an OpenFlow 1.0 based network. Correspondingly, an OpenFlow 1.2 controller may be required to control OpenFlow 1.2 switches and an OpenFlow 1.2 based network. This can lead to network fragmentation by protocols, which can become an acute problem in data networking of SDN for potential customers and the telecommunications industry.